# What reactions involving hydrazine, dinitrogen tetroxide and possibly a contaminant can produce a salt?

Hydrazine $$\ce{N2H4}$$ and dinitrogen tetroxide $$\ce{N2O4}$$ form a hypergolic fuel and oxidizer pair widely used in spacecraft including Akatsuki (あかつき, 暁, "Dawn") also known as the Venus Climate Orbiter (VCO) and Planet-C.

Wikipedia states:

Hydrazine can be monoprotonated to form various solid salts of the hydrazinium cation ($$\ce{N2H5+}$$) by treatment with mineral acids. A common salt is hydrazinium sulfate, $$\ce{[N2H5]HSO4}$$, also called hydrazine sulfate. Hydrazine sulfate was investigated as a treatment of cancer-induced cachexia, but proved ineffective.

Double protonation gives the hydrazinium dication ($$\ce{H3NNH3^2+}$$), of which various salts are known

A comment below the Space SE question How did salt prevent Akatsuki's insertion burn? says:

Every article I see seems to parrot the same thing. I'm guessing this is yet another translation issue (Japanese to English) and the deposits are a hydrazine reaction product... which you could call a "salt". It's an interesting failure case that I hadn't heard of, thanks for the question.

Question: Are there possible reaction products from hydrazine and dinitrogen tetroxide alone that could form an ionic assembly of cations and anions and considered a salt, or would this require some additional contaminant, perhaps water or some organic material to be involved?

• How about with the reaction chamber and nozzle? Of what are they made? Sep 23, 2019 at 3:05
• @DrMoishePippik I've annotated the image from this answer here: i.stack.imgur.com/wMImf.png I've mentioned "water, or some organic material contamination" in the question because these are common contaminations that can come from a wide variety of sources, and I think you are right that can include the reaction chamber and nozzle. Water could be (and probably is) a reaction product and could be plentiful, but my knowledge of chemistry is low and I don't know if that's enough to make something that might be considered a salt.
– uhoh
Sep 23, 2019 at 3:37
• @DrMoishePippik The valve could potentially be pretty far away from them in terms of tubing, but I don't know much about rocket engines or what keeps the high pressure from the combustion chamber from pushing reaction products upstream in this case.
– uhoh
Sep 23, 2019 at 3:37
• BTW, you might enjoy reading *Ignition! An Informal History of Liquid Rocket Propellants," by John D. Clark, library.sciencemadness.org/library/books/ignition.pdf Sep 23, 2019 at 3:45